The invention relates to the field of communications. More specifically, the invention relates to a method and apparatus for restart communication between network elements.
Communication networks are generally comprised of two or more individual network elements, such as a router or switch, coupled together. Network elements generally contain a number of line cards and control cards that are used to transmit data through the network element. The line cards and control cards generally contain a number of circuits to control the transmission of such data.
International-System-International-System (xe2x80x9cIS-ISxe2x80x9d) is a link state interior gateway protocol originally developed for routing ISO/CLNP (xe2x80x9cInternational Organization for Standardization/Connectionless Network Protocolxe2x80x9d) packets among network elements. IS-IS is used to control routing in some networks, and can use a xe2x80x98shortest path firstxe2x80x99 algorithm for determining a particular data route within the network. In particular, network elements typically employ the IS-IS standard to communicate their routing information among one another. Several types of network configurations are supported by IS-IS, e.g., broadcast (network elements are coupled to a single connection medium, such as an Ethernet connection), and point-to-point (network elements are connected to one another directly).
The IS-IS standard utilizes several different types of data packets for the transmission of routing information. For example, hello packets (xe2x80x9cIIHsxe2x80x9d) are used to establish and maintain neighbor adjacency between two network elements. Complete sequence number packets (xe2x80x9cCSNPsxe2x80x9d) contain sequence numbers of all routing information of a network so that an individual network element can determine whether it needs to update its own internal xe2x80x98picturexe2x80x99 of the network. Partial sequence number packets (xe2x80x9cPSNPsxe2x80x9d) contain the sequence numbers for the routing information for one particular network element. Link state packets (xe2x80x9cLSPsxe2x80x9d) contain the actual routing information for a particular network element, i.e., to what other network element(s) or network(s) that it is connected.
Also, xe2x80x98helloxe2x80x99 packets or xe2x80x98heartbeatxe2x80x99 messages are typically sent at regular intervals by network elements to other network elements to tell the recipient network elements that the sending network element is still operational. The recipient network element then expects to receive another xe2x80x98helloxe2x80x99 packet from the sender within the same period of time (which is adjustable). If these xe2x80x98helloxe2x80x99 packets are not received within the time period set, the recipient assumes that the transmitting network element is non-operational for purposes of routing data and accordingly, tears down the communication link between itself and the transmitting network element. Once the transmitting and recipient network element are again able to communicate the communication link between the two must be reconstructed. Moreover, once the communication link is reestablished, the two network elements typically exchange routing information in order to ensure that such information is up-to-date. Disadvantageously, this process of tearing down a communication link, establishing a new communication link and exchanging routing information between the two network elements can be time consuming, thereby potentially causing the loss of data packets within the network that could be transmitted between the two network elements.
A method and apparatus for the restart communication between network elements are described. In one embodiment, a method for restarting communication between a first network element and a second network element in a network comprises transmitting a modified hello packet to the second network element. The modified hello packet includes a time value that is greater than a time value of a hello packet that was transmitted to the second network element prior to International-System-International-System (IS-IS) network communications in the first network element becoming non-operational. The method also including updating routing information within the first network element through transmission of Complete Sequence Number Packets of the IS-IS standard to the second network element, independent of tearing down a communication link between the first network element and the second network element after IS-IS network communications in the first network element have become non-operational.
In an embodiment, a network element includes a memory. Additionally, the network element includes a heartbeat unit coupled to the memory. The heartbeat unit is to transmit a modified heartbeat packet to a different network element in a network. The modified heartbeat packet is to be stored in the memory and is to include a time value that is greater than a time value of a heartbeat packet that is to be transmitted to the different network element prior to International-System-International-System (IS-IS) network communications in the network element becoming non-operational. The network element also includes a reinitialize unit coupled to the heartbeat unit. The reinitialize unit is to update routing information within the network element through transmission of Complete Sequence Number Packets of the International-System-International-System (IS-IS) standard to the different network element, independent of tearing down a communication link between the network element and the different network element after IS-IS network communications the network element have become non-operational.